In recent years, touch panels have come to be widely used as operation portions of mobile devices such as digital cameras, portable video/audio players, mobile telephones, and the like. In a device that is equipped with this sort of touch panel, a user, by touching a function button that is displayed on a display screen of the mobile device, can issue a command to the mobile device to perform a function that corresponds to the function button (refer to Patent Document 1, for example.) In a case where a digital camera is used to record an image, for example, the user searches for a recording start button (called the REC button) on the display screen and starts recording the image by touching the button.